Barbicane calculated the quantity of mercury spilt into the little phial soldered to the lower part of the instrument, and said—
“One hundred and forty degrees centigrade below zero!” (218° Fahr.)
M. Pouillet was right, not Fourier. Such was the frightful temperature of sidereal space! Such perhaps that of the lunar continents when the orb of night loses by radiation all the heat which she absorbs during the fifteen days of sunshine.
XV
Hyperbola or Parabola
Our readers will probably be astonished that Barbicane and his companions were so little occupied with the future in store for them in their metal prison, carried along in the infinitude of ether. Instead of asking themselves where they were going, they lost their time in making experiments, just as if they had been comfortably installed in their own studies.
It might be answered that men so strong-minded were above such considerations, that such little things did not make them uneasy, and that they had something else to do than to think about their future.
The truth is that they were not masters of their projectile—that they could neither stop it nor alter its direction. A seaman can direct the head of his ship as he pleases; an aeronaut can give his balloon vertical movement. They, on the contrary, had no authority over their vehicle. No manoeuvre was possible to them. Hence their not troubling themselves, or “let things go” state of mind.
Where were they at that moment, 8 a.m. during that day called upon earth the sixth of December? Certainly in the neighbourhood of the moon, and even near enough for her to appear like a vast black screen upon the firmament. As to the distance which separated them, it was impossible to estimate it. The projectile, kept up by inexplicable forces, has grazed the north pole of the satellite at less than twenty-five miles’ distance. But had that distance increased or diminished since they had been in the cone of shadow? There was no landmark by which to estimate either the direction or the velocity of the projectile. Perhaps it was going rapidly away from the disc and would soon leave the pure shadow. Perhaps, on the contrary, it was approaching it, and would before long strike against some elevated peak in the invisible atmosphere, which would have terminated the journey, doubtless to the detriment of the travellers.
A discussion began upon this subject, and Michel Ardan, always rich in explanations, gave out the opinion that the bullet, restrained by lunar attraction, would end by falling on the moon like an aerolite on to the surface of the terrestrial globe.
“In the first place,” answered Barbicane, “all aerolites do not fall upon the surface of the earth; only a small proportion do so. Therefore, if we are aerolites it does not necessarily follow that we shall fall upon the moon.”
“Still,” answered Michel, “if we get near enough—”
“Error,” replied Barbicane. “Have you not seen shooting stars by thousands in the sky at certain epochs?”
“Yes.”
“Well, those stars, or rather corpuscles, only shine by rubbing against the atmospheric strata. Now, if they pass through the atmosphere, they pass at less than 16 miles from our globe, and yet they rarely fall. It is the same with our projectile. It may approach very near the moon, and yet not fall upon it.”
“But then,” asked Michel, “I am curious to know how our vehicle would behave in space.”
“I only see two hypotheses,” answered Barbicane, after some minutes’ reflection.
“What are they?”
“The projectile has the choice between two mathematical curves, and it will follow the one or the other according to the velocity with which it is animated, and which I cannot now estimate.”
“Yes, it will either describe a parabola or an hyperbola.”
“Yes,” answered Barbicane, “with some speed it will describe a parabola, and with greater speed an hyperbola.”
“I like those grand words!” exclaimed Michel Ardan. “I know at once what you mean. And what is your parabola, if you please?”
“My friend,” answered the captain, “a parabola is a conic section arising from cutting a cone by a plane parallel to one of its sides.”
“Oh!” said Michel in a satisfied tone.
“It is about the same trajectory that the bomb of a howitzer describes.”
“Just so. And an hyperbola?” asked Michel.
“It is a curve formed by a section of a cone when the cutting plane makes a greater angle with the base than the side of the cone makes.”
“Is it possible?” exclaimed Michel Ardan in the most serious tone, as if he had been informed of a grave event. “Then remember this, Captain Nicholl, what I like in your definition of the hyperbola—I was going to say of the hyper-humbug—is that it is still less easy to understand than the word you pretend to define.”
Nicholl and Barbicane paid no attention to Michel Ardan’s jokes. They had launched into a scientific discussion. They were eager about what curve the projectile would take. One was for the hyperbola, the other for the parabola. They gave each other reasons bristling with x’s. Their arguments were presented in a language which made Michel Ardan jump. The discussion was lively, and neither of the adversaries would sacrifice his curve of predilection.
This scientific dispute was prolonged until Michel Ardan became impatient, and said—
“I say, Messrs. Cosine, do leave off throwing your hyperbolas and parabolas at one’s head. I want to know the only interesting thing about the business. We shall follow one or other of your curves. Very well. But where will they take us to?”
“Nowhere,” answered Nicholl.
“How nowhere?”
“Evidently they are unfinished curves, prolonged indefinitely!”
“Ah, savants! What does it matter about hyperbola or parabola if they both carry us indefinitely into space?”
Barbicane and Nicholl could not help laughing. They cared for art for its own sake. Never had more useless question been discussed at a more inopportune moment. The fatal truth was that the projectile, whether hyperbolically or parabolically carried along,
